The present invention relates generally to a taping method and a taping apparatus for covering a coil having a wire wound about a coil bobbin by a predetermined number of turns with a tape for exterior or interior sheathing. More particularly, the present invention relates to a taping method and a taping apparatus of the foregoing type which assure that each taping operation can be performed automatically and exactly at a predetermined position on the coil bobbin.
As is well known by any expert in the art, each coil winding operation has been hitherto automatically achieved by operating a coil winding machine. In this connection, a taping operation for covering a coil having a wire wound about a coil bobbin by a predetermined number of turns (hereinafter referred to simply as a coil) with a tape for exterior or interior sheathing has been likewise automatically performed with the aid of a taping apparatus adapted to cooperate with the coil winding machine. To cooperate with the taping apparatus, each winding machine is usually equipped with a plurality of tape unwinders which are incorporated in the winding machine.
To facilitate understanding of the present invention, a typical conventional taping apparatus will be described below with reference to FIG. 13 to FIG. 19.
FIG. 13 is a front view of the conventional taping apparatus which is adapted to cooperate with a coil winding machine wherein a base board 110 having a plurality of tape unwinders held thereon (hereinafter referred to simply as a base board) is attached to a three-dimensional displacing mechanism, i.e., a nozzle holder supporting unit 5 operable in three directions comprising a x-coordinate direction, a y-coordinate direction and a z-coordinate direction. FIG. 14 is a plan view of the coil winding machine to which the base board 110 is attached.
Referring to FIG. 14, a plurality of spindles 2 (four spindles in the shown case) are rotationally driven to rotate about a x-coordinate axis. The three-dimensional displacing mechanism, i.e., the nozzle holder supporting unit 5, is constructed such that a plurality of nozzle holders for holding a plurality of nozzles 3 and the base board 110 are arbitrarily displaced relative to the spindles 2 so as to feed a wire to be wound about a coil bobbin in the form of a coil as well as a tape to the coil winding machine and the taping apparatus.
As a tape is unwound from each of four tape supporting units 111 arranged on the base board 110 as shown in FIG. 13, it is fed through feed rollers 112a, 112b, and 112c (as shown in FIG. 15). The foremost end of each tape is then caused to adhere to the outer surface of a coil with the aid of a pad 113, and each coil bobbin 1 is fitted onto a spindle 2 as shown in FIG. 14. It should be noted that each taping operation is performed while the respective spindles 2 are rotated. On completion of the taping operation, the rearmost end of each tape is cut by actuating a cutter (not shown) adapted to be displaced adjacent to each pad 113 in the upward or downward direction.
The three-dimensional displacing mechanism, i.e., the nozzle holder supporting unit 5 is displaceably arranged in such a manner that while a coil winding operation is performed, the base board 110 of the taping apparatus is escapably parted away from the respective spindles 2 so as not to obstruct the coil winding operation, and subsequently, when a taping operation is to be performed, the base board 110 is displaced to come near to the spindles 2.
A mode of operation of the taping apparatus to be performed in cooperation with the coil winding machine including a plurality of tape unwinders will be described below with reference to FIG. 15 to FIG. 19. FIG. 15 to FIG. 19 are fragmentary illustrative views each of which shows the positional relationship among components constituting the taping apparatus as seen from the rear surface side of the base board 110 shown in FIG. 13. Particularly, each of FIG. 15 to FIG. 19 shows the positional relationship between a spindle 2 and the taping apparatus.
A coil bobbin 1 is fixedly mounted on the spindle 2. At this time, a coil wire has been already wound about the coil bobbin 1 by a predetermined number of turns to form a coil 7, and moreover, binding treatment has been already completed for immovably holding the rearmost end of the coil wire.
Referring to FIG. 15 which shows the operative state of the taping apparatus before a taping operation is started, the pad 113 is disposed on a perpendicular plane which intersects the center axis of the spindle 2 at a right angle, and a tape 6 is unwound from the corresponding tape unwinder until the rearmost end of the tape 6 reaches the position coincident with the pad 113. A tape retaining plate 117 serves to thrust the foremost end of the tape 6 against the pad 113 with the fore end part thereof from below.
Next, as shown in FIG. 16, the base board 110 is displaced in the downward direction, and at the same time, the tape retaining plate 117 is parted away from the pad 113 in the rightward direction as seen In the drawing. Subsequently, the pad 113 is lowered by actuating a pneumatic cylinder (not shown) so as to allow the tape 6 to adhere to the outer surface the coil 7 of which wire has been wound about the coil bobbin 1 by a predetermined number of turns. Incidentally, the foremost end of the tape 6 is thrusted against the pad 113 by the tape retaining plate 117 directly before the latter is parted away from the pad 113.
Next, as shown in FIG. 17, the pad 113 is escapably displaced in the upward direction, and the spindle 2 is rotated about the x-coordinate axis in the counterclockwise direction so that the tape 6 is wound about the coil 7. When the spindle 2 is rotated by a predetermined number of revolutions, the rotation of the spindle 2 is stopped.
Subsequently, as shown in FIG. 18, the base board 110 is displaced in the horizontal direction away from the coil bobbin 1 and it is then displaced in the downward direction by a predetermined distance.
At this time, the tape retaining plate 117 comes in contact with the pad 113 so that a part of the tape 6 is firmly clamped between the tape retaining plate 117 and the pad 113. While the foregoing state is maintained, a cutter 114 is displaced in the downward direction to reach the lowermost position represented by phantom lines in order to cut the tape 6 with a sharp edge thereof.
After the tape 6 is cut in that way, a rubber pad 121 arranged independently of the pad 113 is lowered toward the coil 7 until it comes in contact with a preceding layer of tape 6a wound about the coil 7, causing the tape 6 to be firmly thrusted against the coil 7 by the rubber pad 121, as shown in FIG. 19.
When the spindle 2 is rotated in the counterclockwise direction by several turns while the foregoing state is maintained, the tape 6a immovably adheres to the coil 7. It should be added that a rubber pad supporting plate 120 having the rubber pad 121 attached thereto is fixedly secured to the base board 110.
On completion of the taping operation, the base board 110 is displaced in the upward direction to restore the initial state as shown in FIG. 13.
Usually, after each taping operation is completed, a product of coil is detached from the spindle 2. However, in case that the foregoing taping operation is performed in the course of a coil winding operation merely for the purpose of tape insertion for interior sheathing, the coil winding operation is restarted on completion of the preceding taping operation.
With the conventional taping apparatus constructed in the above-described manner, however, it has been found that it has various problems that need to be solved as noted below.
For example, in case the foremost end of a tape fails to adhere to the coil for some reason, a taping operation is incorrectly achieved. In addition, the foremost end of the tape can occasionally adhere to the coil at a position which is offset from the desired position. In extreme case, no taping operation can be achieved with the taping apparatus.
Especially, if a wire winding part of the coil bobbin does not have a circular cross section but has a rectangular section as shown in FIG. 15 to FIG. 19, or in if the wound coil does not exhibit a smooth surface but has some ruggedness, it becomes practically difficult for the foremost end of the tape to correctly adhere to the coil.
In view of the foregoing difficulties, the tape retaining plate 117 is made of an elastic material so as to assure that the foremost end of a tape satisfactorily adheres to the coil regardless of the ruggedness on the coil surface. In addition, it has been found that similar problems arise with the rubber pad 121.
Next, the problems arising at the time of a tape cutting operation will be described below with reference to FIG. 18.
As is apparent from the drawing, the left-hand side of a tape 6 to be cut adheres to the coil bobbin 1, while the right-hand side of the same is firmly clamped between the pad 113 and the tape retaining plate 117. The pad 113 is made of a readily deformable elastic material. Thus, the tape 6 can not firmly be thrusted against the coil on the coil bobbin 1 side. For this reason, there arises an occasion that the cut end of the tape 6 exhibits a rugged shape or after the tape 6 is cut, it is dislocated from the predetermined position in the direction of the width thereof on the pad 113 side, i.e., in the x-coordinate direction.
In addition, the foremost end of the tape 6 can be disconnected from the coil 7 or dislocated from the predetermined position on the coil bobbin 1 for some reason when a taping operation is started while the tape 6 is thrusted against the coil 7 in that way during rotation of the coil bobbin 1 to adhere thereto with an adhesive power of the tape 6. Another problem is that the final state of the taping operation readily becomes unstable.